(a) Frequency distribution of dS values for pairs of genes in fish genomes. The distribution of dS values between Atlantic salmon and rainbow trout orthologues (pink; n=4,854) measures the neutral evolutionary divergence since the two species diverged, while values computed between trout Ss4R paralogues (green; n=6,099) measure the divergence since the more ancient Ss4R. Both events are much younger than the teleost WGD represented by within-species comparisons of paralogues (Ts3R: stickleback, n=1,671; tetraodon, n=974; medaka, n=1,393; zebrafish, n=1,717; trout, n=1,111). Note that in order to represent all the data on the same frequency scale, bin sizes are different for each data set. (b) Evolution of salmonids and the Ss4R timing. The timing of the salmonid radiation (2) and of the speciation of Salmo and Oncorhynchus (2) was based on Crête-Lafreniere et al.16, and the divergence time between Esocidae and Salmonidae (1) was based on Near et al.4.